The present invention relates to a testing apparatus of a magnetic recording medium or a magnetic head, for testing the magnetic recording medium or the magnetic head, which are able in write-in and read-out.
Conventionally, in information processing apparatuses, such as a work station, etc., magnetic recording apparatuses have been used as an outer recording apparatus thereof. It is well-known that, in particular, magnetic disc devices are developed, due to improvement on magnetic substance or on a magnetic head and also due to progress on signal processing technology, in high density of recording and high frequency of recording, as well as in lowering of the price thereof, in recent years, and it bears a burden of high speed and price-lowering of the information processing apparatuses.
Also, the magnetic disc apparatuses are required to be high in the reliability on data being recorded/reproduced, as the outer recording apparatuses, then for testing the magnetic disc or the magnetic head which is applied into a magnetic disc apparatus, a method is often used, in which the testing is carried out by recording/reproducing the test data with use of the magnetic disc or the magnetic head, at the frequency being used in actual practice.
In particular, with the magnetic disc, evaluation and testing are carried out on the disc as an object to be tested, by recording/reproducing the test data which is recorded on the magnetic disc, for example by performing a parametric test, wherein is measured TAA (Track Average Amplitude) as an average amplitude of a disc reproducing signal, such as shown in FIG. 11, as a test parameter recommended by the International Disc Drive Equipment and Materials Association (IDEMA), or PW50 as an average pulse width of the disc reproducing signal at a point of 50% of the average amplitude (TAA).
Also, the evaluation and testing are carried out on the disc as the object to be tested, by performing a certify test, wherein is detected a missing error, in which the amplitude of the disc reproducing signal is reproduced at a unit of data pulse and with an amplitude being too much smaller than the averaged amplitude of the disc reproducing signal when conducting the write-in/read-out of constant frequency data onto the magnetic disc, or a spike error, in which it is reproduced with the amplitude being too much larger than the average amplitude, etc.
FIG. 10 is a drawing for showing the structure of a testing apparatus of the magnetic recording medium or the magnetic head, according to the conventional art.
In the testing apparatus shown in the FIG. 10, first a magnetic disc 101 as the object to be tested is operated to rotate by a disc rotation portion 103, on the contrary to this, a test signal St of frequency fo is generated in a test signal generator circuit 602, so as to be added to a write-in controller circuit 603, wherein a test data is produced in the write-in controller circuit 603, being converted into a write-in current at a certain level in a write-in/read-out amplifier 601, and is written one by one onto the magnetic disc 101 through a R/W head 102 which was acknowledged to be a good-qualified one or was known in the magnetic characteristics thereof.
After completing the write-in, from the track on the magnetic disc 101 onto which the test data is written, the disc reproduction signal is reproduced by the R/W head 102 through the read-in/write-out amplifier 601 as two (2) signals of a positive phase and a negative phase, to be sent to an amplifier (AMP) 604 for level adjusting. Those two (2) disc reproducing signals Ss1 and Ss2 (each being a signal of frequency fo and corresponding to the test signal St), being adjusted in the level there, are inputted into a TAA detection circuit 605, a PW detection circuit 605 and a wave-form comparator circuit 608.
The TAA detection circuit 605 is constructed with using, for example, a voltage comparator circuit (comparator), a controlled current source, a capacitor and a one-turn track integrator circuit (not shown in the figure), wherein the voltage for charging the capacitor and the voltage of the disc reproducing wave-form are compared with, so that an envelope voltage in vicinity of a peak value of the disc reproducing signal is detected while controlling the controlled current source by means of the comparator, so as to charge the capacitor when the voltage of the disc reproducing wave-form is higher than the voltage for charging the capacitor, thereby detecting an integrated value of the envelope voltage for the period of one-turn or one-round of the track by means of the one-turn track integrator circuit.
Conducting dividing process upon the integrated value of the envelope voltage by the time for one-turn of the track, namely by treating averaging process onto the envelope voltage of the disc reproducing signal, the average amplitude value TAA of the disc reproducing signal is detected, so as to be outputted to a slice level producing circuit 606.
Also, a CPU 111 of a controller portion 110 reads the average amplitude value TAA, being the output of the TAA detection circuit, so as to perform measurement of TAA.
In the slice level producing circuit 606, the voltage of 50% with respect to the voltage level of the TAA is set to be a threshold value (i.e., a slice level), as a slice setting 1, to provide an output into a PW detector circuit 607, while, by means of a control signal P outputted by the CPU 111 of the controller portion 110, the voltage value of P % with respect to the voltage level of the TAA is outputted into the wave-form comparator circuit 608, as the slice setting 2.
The PW detector circuit 607 is constructed with, for example a voltage comparator circuit (comparator), a controlled current source, a capacitor and a one-round track integrator circuit (not shown in the figure), wherein the controlled current source is controlled by the comparator, so that the capacitor is charged up only for the time when the disc reproducing signal mentioned above exceeds the slice setting 1, to integrate the capacitor charging voltage for the period of one-turn or one-round of the track in the one-turn track integrator circuit, thereby detecting the integrated value (voltage) of the pulse widths.
The CPU 111 of the controller portion 110 measures the averaged pulse width PW 50 mentioned above, through conducting the dividing process upon the integrated value (voltage) of the pulse widths as the output of the PW detector circuit 607 by the charge current value of the controlled current source and the number of pulses of the disc reproducing signal for the period of one-turn of the track.
The wave-form comparator circuit 608 is constructed with, for example a voltage comparator circuit (comparator), and outputs a comparison result between the voltage value of the above-mentioned disc reproducing signal and the voltage value of the slice setting 2, as a detection signal to an error detection circuit 609. The error detection circuit 609 is constructed with gate circuits, wherein a window pulse is generated for detecting the peak position of the disc reproducing signal pulse, only for a predetermined set period upon the basis of a timing signal T corresponding to each bit of the test data which is sent from the test signal generator circuit 602 mentioned above, while detecting an error, such as the missing error and/or the spike error, etc., from the detection signal as the output of the wave-form comparator circuit 608 and the window pulse, thereby outputting a bit error signal Er to an error memory 610 in synchronism with the each bit of the timing signal T. The error detection circuit 609 also receives the control signal P from the CPU 111 of the controller portion 110, and is changed in the operation condition thereof depending upon the kinds or sorts of errors, so as to detect the each error, such as the missing error and/or the spike error, etc.
The error memory 610 changes the address thereof sequentially, while receiving the timing signal T generated by the test signal generator circuit 602, and also memorizes the error signal Er which is outputted by the error detection circuit 609 into the renewed address, as a defect data, “1” or “0”, sequentially. The CPU 111 reads the contents of the error memory 610 at the time point when the test is completed on all rounds of the magnetic disc 101 as the object to be tested, through a bus into a memory 112, so as to conduct the evaluation of the magnetic disc 101.
Though the above-mentioned is for the magnetic disc as the object to be tested, however when the object to be tested is a magnetic head, the evaluation on the R/W head 102 as the magnetic head is carried out, with using the magnetic disc which was acknowledged to be a good-qualified one or is known in the magnetic characteristics thereof, under the same construction.
Accordingly, with the testing apparatus of the magnetic recording medium or the magnetic head according to the conventional art, shown in the FIG. 10, by performing the circuit operation mentioned above onto the magnetic disc 101 as the object to be tested, it measures the TAA or the PW50, thereby to realizes the prametric test, or it measures the missing error or the spike error, thereby to realize the certify test. As the prior art relating to the present technology, for example, in Japanese Patent Laying-Open No. Hei 10-83501 (1998) is mentioned an outline of the conventional certifier.